MODULE Numeric EXPORTS Main;

IMPORT IO, Fmt, Text;

PROCEDURE isNumeric(s: TEXT): BOOLEAN =
  BEGIN
    FOR i := 0 TO Text.Length(s) DO
      WITH char = Text.GetChar(s, i) DO
        IF i = 0 AND char = '-' THEN
          EXIT;
        END;
        IF char >= '0' AND char <= '9' THEN
          EXIT;
        END;
        RETURN FALSE;
      END;
    END;
    RETURN TRUE;
  END isNumeric;

BEGIN
  IO.Put("isNumeric(152) = " & Fmt.Bool(isNumeric("152")) & "\n");
  IO.Put("isNumeric(-3.1415926) = " & Fmt.Bool(isNumeric("-3.1415926")) & "\n");
  IO.Put("isNumeric(Foo123) = " & Fmt.Bool(isNumeric("Foo123")) & "\n");
END Numeric.